Name: Presence and Uses of Ammonia
Uploaded: 2019-07-19
Duration: 3 min 32 s
Description: Interestingly, smelling salts used to restore senses use ammonia salts because of their pungent odour. Let's learn more about ammonia and its varied uses in...

Question

Explain the construction and working of a Nelson cell.

Accepted Answer

Sodium hydroxide is manufactured from an aqueous solution of sodium chloride called brine using the Nelson cell by the electrolysis process. It is also called Chlor-Alkali process. The construction and working of a Nelson cell are as given below:

Construction of a Nelson cell: Nelson cell consists of a perforated steel U-tube insulated by asbestos lining. This U-tube acts as a cathode. The U-shaped vessel is provided with an inlet and an outlet. Through the inlet, a brine solution is introduced into the U-tube. A graphite rod is suspended in the CT tube. This acts as an anode. This cell is suspended in a rectangular steel tank. This is also provided with an outlet and a side tube.

Working of a Nelson cell: On passing electricity through the brine solution, sodium chloride dissociates to give ${Na}^{+}$ and ${Cl}^{-}$ ions.

$NaCl \to {Na}^{+} + {Cl}^{-}$

Chloride ions get discharged at the anode liberating chlorine gas. This is collected through an outlet provided for the U tube.

$2 {Cl}^{-} \to {Cl}_{2} + 2 e^{-}$

Steam is allowed to enter the rectangular steel tank. Sodium ions penetrate through asbestos and react with steam thereby forming sodium hydroxide:

${Na}^{+} + H_{2} O \to NaOH + H^{+}$

$H^{+}$ ions get discharged at the cathode where they undergo reduction to liberate hydrogen gas which is collected through the outlet provided for in the rectangular steel tank:

$2 H^{+} + 2 e^{-} \to H_{2}$

Explain the construction and working of a Nelson cell.

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